Phase modulation indicator



Feb. 13, 1940.

' F. GUTZ-MANN 2,189,896 PHASEMODULATION INDICATOR Filed Sept. 14, 1937 Generator Patented, Feb. 13, 1940 UNITED STATES;

Fritz Gutzmann, Berlin, Germany, assignor to Lorenz Aktiengesellschaft, Berlin-Tempelhof,.; '1"; LorenzwegGermany, a, company' q I Application se ester 14,1931 Serial N0.9163,770-

In Germanyseptember1451936 l v 2 Claims. 01. 250- 7) to the disturbed It, has been proposed to measure the phase modulation of high frequency transmitters by superimposing upon the phase modulated alternating voltage a non-modulated alternatingvoltage of the same frequency and by using the variation of the rectified-combination voltagewor beat frequency inorder to measure the phase modulation. In this way the phase modulation is converted intoan effective amplitude modulation for the purpose of measurement. This conversion may be accomplished. in a known manner as explained on pages '70 and Hot vol ume 3/4 of Lorenz-Berichten 1936, in an article entitled Ein neues Gerat zur Messung von Phasenmodulaticnen by F. Gutzmann. A car- 'rier wave of correct phase and amplitude is added to the phase modulated carrier so that the resultant carrier is in phase with the side bands created by the phase modulation, so that the modulations appear as amplitude variations of the resultant added carriers. The manner in which adjustment of the carrier frequency added to the modulated wave. is cbtained is not a fea ture of my invention and therefore is not "illus-,

trated in detail, since known means are avail-- In measuring arrange merits of this kind difficulties arise through the able for this purpose.

fact that the frequency to be investigated reacts upon the superimposed frequency by influencing the generator of the constant or superimgenerator in tube type. l i In order to avoid this disadvantage it is pro posed by the invention to convey the two alterhating voltages to a bridge arrangementwhich is given a specialadjustment with respect to these voltages, as will be understood from. the following description and be particularly pointed 40 out in the appended claims, reference being had to the accompanying drawing which shows a wiring diagram of one embodiment of the invention. 7 In this drawing, 1 denotes a generator for producing the constant superimposed frequency ulated frequency. These two alternating voltages are conveyed to abridge t that comprises "four condensers i, 5, 5, 5?, two inductanc'es 8, 9, an ohmic resistance It and arectifier circuit ll connected in'parallel with condenser 5. Circuit It comprises an ohmic resistance i2, a rectiiying valve tube it and a current-measuring device or ammeterl The phase modulated or disturbed alternating voltagearriving from the current source '2 is supplied to points a, b of bridge 3 while the constant alternating voltage from generator I is supplied to the bridge points 0, :1. Bridge 3 is so adjusted that with respect posed frequency at the output side thereof, this most cases be'ing of the electron while 2 designates the source of thephase-mod quency.

frequency the points. 0,,d areequipotential and cophasal such relationship also applying to the points a, b, as regards' 'thc constant frequency. In order to obtain thisadjustmen'tall the operative members of thebridge are variable. The currents rectified by tube I3 are conveyed through filtering means l5 to an indicating instrument It, for instance an ampli- Instrument. l6 may be such :10

fying voltmeter.

that the disturbing phaseimodulation can .be,

read off, or maybean acousticor recording device.

."-'The novelarrangement allows ofindicating both phase modulation and frequency module; I tion, sincethese twoare equivalent in physical relation.

It is of importancethat in contra-distinction to other arrangements forfmeasuring the phase modulation the no-vel arrangement actsto indi The supply' leads llqare preferably con 1: stituted bye cable with unipolar grounding.

cate the entirelowflfrequency spectrum of the phase modulating frequencies, thus enabling the measurement to be madewith the aid of an audio filter adequate to the sensitiveness "of thehuman ear. Touse a device of this character isabsolutely necessary for ascertaining disturbing phase modulations, theactualnieasuremeht of ment. H 3

What is claimed is: 1. A circuit arrangement these being only enabled by thenovel arrange I Y for frequency transmitters which comprises two alternating current sources one of which is of-a, constant frequency value while the energy from thenot her 35 is subject to disturbances, a bridge comprising ;v

four impedance arms to which {these two current sources are connected, one source beingyjconnect'ed to two opposing points of this bridge and the'other connected to. two other opposing is joined andequipotential alsoat the points to l which the, other current sourceis joined, means bridged across one of said'impe'dance arms for rectifying the energy from r the said current sources. and a resistance simulating the impedanceof said means for rectifying bridged across an associated arm of said bridge. f

2. An arrangement according to claim. 1, said -means for rectifying operating on the beat fre quency formed by the energy from the twoscur rent sources, and an instrument connected to said rectifyingmeans for indicating disturbing phase modulation contained in this beat free H Farm;

points thereof, means forjadjusting the bridge,

ctheadjusted bridge being equipotential at the points to which one of the said current sources 

